Mohs micrographic surgery for BCCs and SCCs involves precise excision of the cancer with minimal damage to the surrounding normal skin. Conventionally, precise excision is guided by histopathologic examination for cancer margins in the excised tissue slices during Mohs surgery. Typically, 2–4 slices are excised, and there is a waiting time of 10–30 minutes for the surgeon and patient while each slice is being processed.
Confocal reflectance microscopes can noninvasively image nuclear and cellular detail in living skin to provide images of tissue sections, such a microscope is described in U.S. Pat. No. 5,880,880. The contrast in the images is believed to be due to the detected variations in the singly back-scattered light caused by variations in refractive indices of tissue microstructure. Within the epidermal (basal and squamous) cells, the cytoplasm appears bright and the nuclei as dark ovals. The underlying dermis consists of collagen bundles and that, too, appears bright with dark spaces in-between. Thus, when neoplastic epidermal cells invade the dermis as in BCCs and SCCs, confocal detection of the cancers is very difficult because the cells and nuclei lack contrast relative to the surrounding normal dermis.
Acetic acid (vinegar) has been used as an image enhancement agent which enhances the back-scatter of light from certain cells. This is described, for example, in U.S. Pat. No. 5,733,739. When a tissue is illuminated with light of one polarization and a reflected image is detected via light of cross polarization the contrast of certain cells in the detected image is enhanced, when the tissue is treated by acetic acid, especially when the image is viewed via cross-polarized light in a confocal microscope. Such a system is described in the above referenced International Application No. PCT/US00/07008.